xref: /openbsd/gnu/usr.bin/perl/lib/strict.pm (revision 3d61058a) 
1package strict;
2
3$strict::VERSION = "1.13";
4
5my ( %bitmask, %explicit_bitmask );
6
7BEGIN {
8    # Verify that we're called correctly so that strictures will work.
9    # Can't use Carp, since Carp uses us!
10    # see also warnings.pm.
11    die sprintf "Incorrect use of pragma '%s' at %s line %d.\n", __PACKAGE__, +(caller)[1,2]
12        if __FILE__ !~ ( '(?x) \b     '.__PACKAGE__.'  \.pmc? \z' )
13        && __FILE__ =~ ( '(?x) \b (?i:'.__PACKAGE__.') \.pmc? \z' );
14
15    %bitmask = (
16        refs => 0x00000002,
17        subs => 0x00000200,
18        vars => 0x00000400,
19    );
20
21    %explicit_bitmask = (
22        refs => 0x00000020,
23        subs => 0x00000040,
24        vars => 0x00000080,
25    );
26
27    my $bits = 0;
28    $bits |= $_ for values %bitmask;
29
30    my $inline_all_bits = $bits;
31    *all_bits = sub () { $inline_all_bits };
32
33    $bits = 0;
34    $bits |= $_ for values %explicit_bitmask;
35
36    my $inline_all_explicit_bits = $bits;
37    *all_explicit_bits = sub () { $inline_all_explicit_bits };
38}
39
40sub bits {
41    my $bits = 0;
42    my @wrong;
43    foreach my $s (@_) {
44        if (exists $bitmask{$s}) {
45            $^H |= $explicit_bitmask{$s};
46
47            $bits |= $bitmask{$s};
48        }
49        else {
50            push @wrong, $s;
51        }
52    }
53    if (@wrong) {
54        require Carp;
55        Carp::croak("Unknown 'strict' tag(s) '@wrong'");
56    }
57    $bits;
58}
59
60sub import {
61    shift;
62    $^H |= @_ ? &bits : all_bits | all_explicit_bits;
63}
64
65sub unimport {
66    shift;
67
68    if (@_) {
69        $^H &= ~&bits;
70    }
71    else {
72        $^H &= ~all_bits;
73        $^H |= all_explicit_bits;
74    }
75}
76
771;
78__END__
79
80=head1 NAME
81
82strict - Perl pragma to restrict unsafe constructs
83
84=head1 SYNOPSIS
85
86    use strict;
87
88    use strict "vars";
89    use strict "refs";
90    use strict "subs";
91
92    use strict;
93    no strict "vars";
94
95=head1 DESCRIPTION
96
97The C<strict> pragma disables certain Perl expressions that could behave
98unexpectedly or are difficult to debug, turning them into errors. The
99effect of this pragma is limited to the current file or scope block.
100
101If no import list is supplied, all possible restrictions are assumed.
102(This is the safest mode to operate in, but is sometimes too strict for
103casual programming.)  Currently, there are three possible things to be
104strict about:  "subs", "vars", and "refs".
105
106=over 6
107
108=item C<strict refs>
109
110This generates a runtime error if you
111use symbolic references (see L<perlref>).
112
113    use strict 'refs';
114    $ref = \$foo;
115    print $$ref;	# ok
116    $ref = "foo";
117    print $$ref;	# runtime error; normally ok
118    $file = "STDOUT";
119    print $file "Hi!";	# error; note: no comma after $file
120
121There is one exception to this rule:
122
123    $bar = \&{'foo'};
124    &$bar;
125
126is allowed so that C<goto &$AUTOLOAD> would not break under stricture.
127
128
129=item C<strict vars>
130
131This generates a compile-time error if you access a variable that was
132neither explicitly declared (using any of C<my>, C<our>, C<state>, or C<use
133vars>) nor fully qualified.  (Because this is to avoid variable suicide
134problems and subtle dynamic scoping issues, a merely C<local> variable isn't
135good enough.)  See L<perlfunc/my>, L<perlfunc/our>, L<perlfunc/state>,
136L<perlfunc/local>, and L<vars>.
137
138    use strict 'vars';
139    $X::foo = 1;	 # ok, fully qualified
140    my $foo = 10;	 # ok, my() var
141    local $baz = 9;	 # blows up, $baz not declared before
142
143    package Cinna;
144    our $bar;			# Declares $bar in current package
145    $bar = 'HgS';		# ok, global declared via pragma
146
147The local() generated a compile-time error because you just touched a global
148name without fully qualifying it.
149
150Because of their special use by sort(), the variables $a and $b are
151exempted from this check.
152
153=item C<strict subs>
154
155This disables the poetry optimization, generating a compile-time error if
156you try to use a bareword identifier that's not a subroutine, unless it
157is a simple identifier (no colons) and that it appears in curly braces,
158on the left hand side of the C<< => >> symbol, or has the unary minus
159operator applied to it.
160
161    use strict 'subs';
162    $SIG{PIPE} = Plumber;   # blows up
163    $SIG{PIPE} = "Plumber"; # fine: quoted string is always ok
164    $SIG{PIPE} = \&Plumber; # preferred form
165
166=back
167
168See L<perlmodlib/Pragmatic Modules>.
169
170=head1 HISTORY
171
172C<strict 'subs'>, with Perl 5.6.1, erroneously permitted to use an unquoted
173compound identifier (e.g. C<Foo::Bar>) as a hash key (before C<< => >> or
174inside curlies), but without forcing it always to a literal string.
175
176Starting with Perl 5.8.1 strict is strict about its restrictions:
177if unknown restrictions are used, the strict pragma will abort with
178
179    Unknown 'strict' tag(s) '...'
180
181As of version 1.04 (Perl 5.10), strict verifies that it is used as
182"strict" to avoid the dreaded Strict trap on case insensitive file
183systems.
184
185Beginning with Perl 5.12, use of "use VERSION" (where VERSION >= 5.11.0) now
186lexically enables strictures just like "use strict" (in addition to the normal
187"use VERSION" effects and features.)  In other words, "use v5.011" or higher
188now implies "use strict" automatically, as noted in
189L<perl5120delta/"Implicit strictures"> and L<C<use VERSION>|perlfunc/use VERSION>.
190
191=cut
192